More like an accessibility setting that has widespread utility (there are several others, e.g. iOS has built-in background noise generators in accessibility)

That said, tapping on the back of the phone didn’t register consistently enough for me to utilize. I tried setting flashlight to that action. When I wanted it to work it wouldn’t. Then when I would be absentmindedly tapping it would activate.

It’s an “accessibility” feature. You can assign an action to double and triple tap. But it’s very inconsistent. It doesn’t work half the time and it will trigger randomly if you move your phone funny.

Also, since I had an atari st as my first 'serious" computer, I loved the B&W monitor and b&W GEM.

I'm still looking for a way to preserve the low-color feel for my macbooks and mac desktops. Also I love the idea of low-dopamine UIs in principle.

For same reasons as the original author, I find myself to abandon the B&W mode and then do not turn it back on later.

I'd envision OS layer that handles the desktop, finder and apps, and an API that apps like browsers can use, e.g. in chrome extensions.

Anyone here aware of work in that area?

It’s in the accessibility settings. You can assign an action for double or triple tap.